Detection of calretinin expression in abnormal immature Sertoli cells in non-obstructive azoospermia

Molecular mechanisms of cellular dysfunction in testes from men with non-obstructive azoospermia

Male factor infertility affects 50% of infertile couples worldwide; the most severe form, non-obstructive azoospermia (NOA), affects 10-15% of infertile males. Treatment for individuals with NOA is limited to microsurgical sperm extraction paired with in vitro fertilization intracytoplasmic sperm injection. Unfortunately, spermatozoa are only retrieved in ~50% of patients, resulting in live birth rates of 21-46%. Regenerative therapies could provide a solution; however, understanding the cell-type-specific mechanisms of cellular dysfunction is a fundamental necessity to develop precision medicine strategies that could overcome these abnormalities and promote regeneration of spermatogenesis. A number of mechanisms of cellular dysfunction have been elucidated in NOA testicular cells. These mechanisms include abnormalities in both somatic cells and germ cells in NOA testes, such as somatic cell immaturity, aberrant growth factor signalling, increased inflammation, increased apoptosis and abnormal extracellular matrix regulation. Future cell-type-specific investigations in identifying modulators of cellular transcription and translation will be key to understanding upstream dysregulation, and these studies will require development of in vitro models to functionally interrogate spermatogenic niche dysfunction in both somatic and germ cells.

Seminal calbindin 2 level in azoospermia and oligoasthenoteratozoospermia and its correlation with seminal and hormonal parameters

OBJECTIVES

We aimed to assess seminal calbindin 2 (CALB 2) expression in men with different semen parameters as well as its correlation with reproductive hormones in azoospermic patients and different semen parameters in oligoasthenoteratozoospermic patients. CALB 2 is also known as calretinin and 29 kDa calbindin.

MATERIALS AND METHODS

This prospective study was performed on 96 cases from the andrology outpatient clinic divided into 3 groups as follows: group 1 including 32 non obstructive azoospermic (NOA) patients, group 2 including 32 patients with oligoasthenoteratozoospermia (OAT), and Group 3 including normozoospermic individuals as controls. Semen analysis and estimation of seminal CALB 2 concentrations by enzyme linked immunosorbent assay (ELISA) technique were performed for all participants. Reproductive hormones were measured in nonobstructive NOA patients.

RESULTS

The mean seminal CALB 2 level was higher in OAT patients compared to NOA patients and controls (7.8 ± 1.30 ng/ml, 7.3 ± 0.80 and 7.4 ± 1.0, respectively). Furthermore, the study had shown strong positive correlations between CALB 2 and sperm normal forms in controls and OAT patients. In contrast, there was no significant correlation between seminal CALB 2 and any of the reproductive hormones measured in NOA patients.

CONCLUSIONS

Seminal CALB 2 may play a role in increasing the abnormal forms in OAT patients.

Seminal Calbindin 2 in Infertile Men With Varicocele: A Prospective Comparative Study

The present study compared seminal calbindin 2 (CALB 2) levels and semen parameters in men with and without varicocele. CALB 2 is also known as calretinin and 29 kDa calbindin. The study was a case-control study conducted from April (2021) to March (2022) in the andrology department at Beni-Suef University hospital. The study included four matched groups: group (I) were controls (fertile normozoospermic men without varicocele) (n=24). Group (II) were fertile normozoospermic men with varicocele (n=24). Group (III) were infertile oligoasthenoteratozoospermia (OAT) men without varicocele (n=24). Group (IV) were infertile OAT men with varicocele (n=24). The lowest levels of seminal CALB 2 were found in patients with severe oligozoospermia which showed a statistically significant difference when compared to seminal CALB 2 in patients with normal, mildly low, or moderately low sperm counts. There were significant negative correlations between sperm concentration, sperm motility and percentage of normal sperm forms and seminal CALB 2. Seminal plasma CALB 2 may play a role in the negative impact of varicocele on the semen parameters especially sperm concentration, sperm motility and percentage of sperm normal forms. Future studies are needed to verify these findings.

Sertoli and Germ Cells Within Atrophic Seminiferous Tubules of Men With Non-Obstructive Azoospermia

BACKGROUND

Infertile men with non-obstructive azoospermia (NOA) have impaired spermatogenesis. Dilated and un-dilated atrophic seminiferous tubules are often present in the testes of these patients, with the highest likelihood of active spermatogenesis in the dilated tubules. Little is known about the un-dilated tubules, which in NOA patients constitute the majority. To advance therapeutic strategies for men with NOA who fail surgical sperm retrieval we aimed to characterize the spermatogonial stem cell microenvironment in atrophic un-dilated tubules.

METHODS

Testis biopsies approximately 3x3x3 mm³ were obtained from un-dilated areas from 34 patients. They were classified as hypospermatogenesis (HS) (n=5), maturation arrest (MA) (n=14), and Sertoli cell only (SCO) (n= 15). Testis samples from five fertile men were included as controls. Biopsies were used for histological analysis, RT-PCR analysis and immunofluorescence of germ and Sertoli cell markers.

RESULTS

Anti-Müllerian hormone mRNA and protein expression was increased in un-dilated tubules in all three NOA subtypes, compared to the control, showing an immature state of Sertoli cells (p<0.05). The GDNF mRNA expression was significantly increased in MA (P=0.0003). The BMP4 mRNA expression showed a significant increase in HS, MA, and SCO (P=0.02, P=0.0005, P=0.02, respectively). The thickness of the tubule wall was increased 2.2-fold in the SCO-NOA compared to the control (p<0.05). In germ cells, we found the DEAD-box helicase 4 (DDX4) and melanoma-associated antigen A4 (MAGE-A4) mRNA and protein expression reduced in NOA (MAGE-A: 46% decrease in HS, 53% decrease in MA, absent in SCO). In HS-NOA, the number of androgen receptor positive Sertoli cells was reduced 30% with a similar pattern in mRNA expression. The γH2AX expression was increased in SCO as compared to HS and MA. However, none of these differences reached statistical significance probably due to low number of samples.

CONCLUSIONS

Sertoli cells were shown to be immature in un-dilated tubules of three NOA subtypes. The increased DNA damage in Sertoli cells and thicker tubule wall in SCO suggested a different mechanism for the absence of spermatogenesis from SCO to HS and MA. These results expand insight into the differences in un-dilated tubules from the different types of NOA patients.

Common markers of testicular Sertoli cells

INTRODUCTION

Sertoli cells play central roles in the development of testis formation in fetuses and the initiation and maintenance of spermatogenesis in puberty and adulthood, and disorders of Sertoli cell proliferation and/or functional maturation can cause male reproductive disorders at various life stages. It's well documented that various genes are either overexpressed or absent in Sertoli cells during the conversion of an immature, proliferating Sertoli cell to a mature, non-proliferating Sertoli cell, which are considered as Sertoli cell stage-specific markers. Thus, it is paramount to choose an appropriate Sertoli cell marker that will be used not only to identify the developmental, proliferative, and maturation of Sertoli cell status in the testis during the fetal period, prepuberty, puberty, or in the adult, but also to diagnose the mechanisms underlying spermatogenic dysfunction.

AREAS COVERED

In this review, we principally enumerated 5 categories of testicular Sertoli cell markers - including immature Sertoli cell markers, mature Sertoli cell markers, immature/mature Sertoli cell markers, Sertoli cell functional markers, and others.

EXPERT OPINION

By delineating the characteristics and applications of more than 20 Sertoli cell markers, this review provided novel Sertoli cell markers for the more accurate diagnosis and mechanistic evaluation of male reproductive disorders.

Transcriptome analysis of fetal rat testis following intrauterine exposure to the azole fungicides triticonazole and flusilazole reveals subtle changes despite adverse endocrine effects

Azoles are used in agriculture and medicine to combat fungal infections. We have previously examined the endocrine disrupting properties of the agricultural azole fungicides triticonazole and flusilazole. Triticonazole displayed strong androgen receptor (AR) antagonism in vitro, whereas in utero exposure resulted in anti-androgenic effects in vivo evidenced by shorter anogenital distance (AGD) in fetal male rats. Flusilazole displayed strong AR antagonism, but less potent than triticonazole, and disrupted steroidogenesis in vitro, whereas in utero exposure disrupted fetal male plasma hormone levels. To elaborate on how these azole fungicides can disrupt male reproductive development by different mechanisms, and to investigate whether feminization effects such as short AGD in males can also be detected at the transcript level in fetal testes, we profiled fetal testis transcriptomes after in utero exposure to triticonazole and flusilazole by 3'Digital Gene Expression (3'DGE). The analysis revealed few transcriptional changes after exposure to either compound at gestation day 17 and 21. This suggests that the observed influence of flusilazole on hormone production may be by directly targeting steroidogenic enzyme activity in the testis at the protein level, whereas observations of shorter AGD by triticonazole may primarily be due to disturbed androgen signaling in androgen-sensitive tissues. Expression of Calb2 and Gsta2 was altered by flusilazole but not triticonazole and may pinpoint novel pathways of disrupted testicular steroid synthesis. Our findings have wider implication for how we integrate omics data in chemical testing frameworks, including selection of non-animal test methods and building of Adverse Outcome Pathways for regulatory purposes.

Characterization and potential roles of calretinin in rodent spermatozoa

Calretinin has been detected in various excitable cells but the presence and putative roles of such a calcium-binding protein has never been characterized in sperm. Epididymal spermatozoa were collected from C57Bl6 (wild-type, WT) or calretinin knockout (CR^-/-) mice and Wistar rats. A specific staining for calretinin was detected by immunofluorescence in the principal piece of the flagellum, both in WT mouse and rat spermatozoa. Western blots confirmed the expression of calretinin in rat and WT spermatozoa as well as its absence in CR^-/- mice. No significant difference was observed in the spontaneous acrosome reaction between WT and CR^-/- sperm. The addition of the calcium-ionophore A-23187, Thapsigargin or Progesterone to WT or CR^-/- incubated spermatozoa induced increases in the acrosome reaction but the stimulatory effects were identical in both genotypes. Motility measurements assessed by computer-assisted sperm analysis indicated that, under basal non-stimulatory conditions, CR^-/- sperm exhibited a lower curvilinear velocity and a smaller lateral head movement amplitude, although no difference was observed for the beat cross frequency. After incubation with 25 mM NH₄Cl, the curvilinear velocity, the amplitude of the lateral head movement and the hyperactivation were increased, while the beat cross frequency was decreased, in both genotypes. Evaluation of the in vivo fertility potential indicated that the CR^-/- litter sizes were clearly reduced compared to the WT litter sizes. Our study describes, for the first time, the expression of calretinin in sperm. These data extend the potential implication of calcium-binding proteins in the sperm calcium-signaling cascade and bring new insights into the understanding of sperm physiology.

[The Sertoli cell]

The Sertoli cell is essential for the formation and functioning of the testis. This is the first cell to differentiate into the initially bipotential genital ridge and is the only somatic cell present in seminiferous tubules. Maturation involves the loss of proliferative capacity, formation of intercellular tight junctions and the appearance of some specific markers. We can consider schematically two distinct roles associated with different features: a process of sexual differentiation with testicular formation and a role in spermatogenesis allowing the germ cells progression into sperm through close contact in the seminiferous tubules. These events, separated in time, are in fact intimately linked.

Reduced numbers of Sertoli, germ, and spermatogonial stem cells in impaired spermatogenesis

A key step in the investigation of male infertility is the appropriate classification of impaired spermatogenesis. In this study, we precisely identified Sertoli and distinct germ-cell types in the rat, the mouse, and in the human testis. As a proof of principle, we studied testis biopsy samples from azoospermic patients with defined spermatogenic defects. Remarkably, we found that already the numbers of Sertoli cells, spermatogonia and a subset of spermatogonia including stem cells are significantly reduced in patients with maturation arrest at the level of primary spermatocytes (n=33) compared with patients with histologically normal spermatogenesis (n=33). In patients with hypospermatogenesis (n=44) a significant reduction of spermatogonial cell numbers was observed. The numbers of primary and diplotene spermatocytes were reduced by 84%. However, the strongest reduction (96%) was revealed in the numbers of spermatids in patients with maturation arrest. In contrast, patients with hypospermatogenesis showed only modestly reduced numbers of spermatocytes and spermatids compared with normal spermatogenesis. No correlation was found with age or obstruction. For a detailed analysis of the patients, we distinguished between 'pool of founder cells'-related deficiencies (reduced numbers of Sertoli cells, spermatogonia, and spermatogonial stem cells) and 'meiotic' deficiencies (reduced numbers of spermatocytes, meiotic divisions, and spermatids). Interestingly, patients with maturation arrest showed meiotic deficiencies (36%), while the majority additionally demonstrated deficiencies in the founder pool (58%). In contrast, patients with normal spermatogenesis most often had no deficiencies at all (45%) or founder pool-related deficiencies (33%) but an apparently normal meiosis. This is the first report showing that many infertile patients face besides meiotic defects the problem of reduced numbers of Sertoli cells, spermatogonia, and spermatogonial stem cells.

A novel assessment of the quality of immunohistostaining overcomes the limitations of current methods

Quality assurance has become an integral part of surgical pathology. Despite the development of interdisciplinary quality systems, however, the means for objective analysis in surgical pathology are limited. Immunohistostaining is a multi-factorial procedure that depends on the quality of reagents and antibodies employed in the process and on technical methodology. In the present study, we aim to establish a straightforward procedure for objective quality evaluation of the components involved in immunohistostaining. The quality of two of these components, the primary antibody and the automated staining device, was assessed by employing each component from two different sources, one serving as the test substance and the second as the reference. Assessment was performed by at least two pathologists in a blinded fashion using pre-established quality criteria and scores. The quality analysis of two automated devices revealed a significant difference between the reference and tested devices (3.5+/-1.7 and 4.2+/-1.5, respectively, P>0.05), while the analysis of two selected antibodies did not reveal any statistical difference. The described method provided objective quality assessment of selected components affecting immunohistostaining by elaborating numeric values that enabled statistical analysis. This approach is applicable to any given component in various surgical pathology procedures.